Natural leather is the traditional material for producing quality leathergoods, such as footwear, waist belts, carpenter aprons, tool pouches, safety belts, small personal leathergoods, and the like. However, natural leather presents technical difficulties in manufacture, economic difficulties in marketing, and durability problems in use of these goods. Wide quality variations among hides, and defects within a hide cause technical difficulties in cutting hides in an economical manner, and the different sizes and shapes do not allow for automatic cutting of the hides. In addition to the difficulties of variations and defects, the rapidly escalating price of untanned hides and tanning labor and chemical costs have markedly increased the cost of leather in recent years. Thus, leather has become a very expensive component of finished goods. Moreover, leather's susceptibility to hydrolytic degredation has limited its application or utility in certain service environments.
For these and other reasons, considerable efforts have been made in the art to produce man-made leather substitutes. These substitute materials are commonly referred to, collectively, as artificial leathers, although these substitute materials may vary widely in their properties and some of the substitute materials have few properties in common with leather. In one respect, these differences between the properties of leather and the substitute materials are the results of efforts to provide properties which are not provided by leather and, in another respect, these differences are the results of the inability in the art to produce certain of the desirable properties of leather.
There have been two major approaches in the art to producing leather substitute materials. One major approach provides a permeable material while the other major approach provides an impermeable material. The permeable materials are based on a microporous film of up to 30 mils thick being disposed on a permeable substrate. The well-known CORFAM is an example thereof. The use of an impermeable film on a permeable or impermeable substrate has been more accepted commercially, and an example thereof is expanded PVC substitute materials. In the CORFAM-type material, a combination of a needled non-woven substrate and a woven element is used to provide the required strengths, since the decorative permeable film provides very little strength to that composite. On the other hand, the expanded PVC-type material relies to a significant degree on the relatively thick impermeable decorative film for strength and the textile substrate is a relatively light woven or non-woven substrate. The CORFAM-type material adsorbs moisture to a very slight extent, but being permeable is able to transmit that moisture even during use, while the expanded PVC-type material must adsorb the moisture during use and release the moisture during non-use from the undersurface thereof. The CORFAM-type material is subject to scuffing which is essentially non-repairable. On the other hand, the expanded PVC-type material has a relatively thick and somewhat spongy skin coat layer. This resists scuffing, but once scuffed, is effectively non-repairable.
Thus, the art has not produced a totally satisfactory substitute material and the difficulties associated with these materials inhibited wide acceptance thereof. Many efforts have been made in the art to mitigate these problems and a most significant advance in the art in this regard is disclosed in U.S. Pat. No. 3,817,820, issued on June 28, 1974 to Alexander M. Smith, II. That patent discloses that the axis of flexure of a needled textile fabric may be shifted toward the face surface by forming a web of loosely matted fibers (a conventional carded structure) where the web has a needle pick-up gradient from the back surface to the face surface, e.g., by using layers of fibers with different fiber deniers, and then needling the web sufficiently to produce an integral structure of coherent entangled fibers and to produce an overall bulk density of at least 6 pounds per cubic foot. It is taught that the high number of needle punches per square inch of the web with the needle pick-up gradient produces a bulk density at or near the back surface which is lower than the bulk density at or near the face surface and, hence, the axis of flexure of the needled structure is shifted toward the face surface, which in turn produces flexure properties in the substitute material which are similar to the corresponding leather flexure properties, while also providing a permeable material.
While the method of the Smith patent provides a leather substitute material which is superior to other substitute materials, it requires the use of multiple carding machines or multiple passes with a single machine to form and stratified web of fibers for needling. Carding machines are expensive capital equipment and require considerable factory floor space. Further, these machines must be properly supervised during the laying of the web for needling to insure that the required stratification of fibers is achieved. Thus, the use of the multiple carding machines or multiple passes thereby inherently increases the capital costs and production costs of the leather substitute material produced by that method. Therefore, it would be of decided advantage in the art if the functional advantages of the substitute of the Smith patent could be maintained while eliminating the necessity for multiple carding machines in making the needled substrate.